On Thu, 2012-10-04 at 10:46 -0700, Greg Kroah-Hartman wrote: > On Thu, Oct 04, 2012 at 12:11:01PM +0800, Huacai Chen wrote: > > Hi, Greg > > > > I found that Linux-3.5.5 accept this commit "sched: Add missing call > > to calc_load_exit_idle()" but I think this isn't needed. Because > > "5167e8d5417b sched/nohz: Rewrite and fix load-avg computation -- > > again not fully applied" is true for 3.6 branch, but not for 3.5 > > branch. > > But 5167e8d5417b is in 3.5, so shouldn't this commit still be necessary? > > > In 3.5 branch, calc_load_exit_idle() is already called in > > tick_nohz_idle_exit(), it doesn't need to be called at > > tick_nohz_update_jiffies() again. In 3.6 branch, some code of > > tick_nohz_idle_exit() is splitted to tick_nohz_restart_sched_tick() > > and calc_load_exit_idle() is missing by accident, so commit "sched: > > Add missing call to calc_load_exit_idle()" is needed. > > So this really should be dropped from 3.5? Charles, Peter, Ingo, any > thoughts here?
Bah, lots of code movement there recently.. let me try and untangle all that afresh.. /me checks out v3.5.5. OK, assuming ->tick_stopped means what the label says, then we only want to call calc_load_enter_idle() when it flips to 1 and calc_load_exit_idle() when it flips back to 0, such that when an actual tick happens its got correct state. Now the actual patch "5167e8d5417b sched/nohz: Rewrite and fix load-avg computation -- again not fully applied" modifies tick_nohz_restart_sched_tick() which doesn't appear to exist in v3.5.5 and the patch fobbed it into tick_nohz_update_jiffies() which is called from interrupt entry when nohz-idle so that the interrupt (and possible tailing softirq) see a valid jiffies count. However, since we don't restart the tick, we won't be sampling load muck and calling calc_load_exit_idle() from there is bound to confuse state. I hope.. damn this code ;-) I can't find wtf went wrong either, the initial patch 5167e8d5417bf5c contains both hunks, but in that case the fixup 749c8814f0 doesn't make sense, not can I find anything in merge commits using: git log -S calc_load_exit_idle kernel/time/tick-sched.c /me puzzled -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
